1. Field of the Invention
The present invention relates to air pumps and more particularly, to a portable air pump equipped with a pressure gauge that is receivable by biasing.
2. Description of the Related Art
Conventional portable air pumps are commonly designed to be operated by both hands. During operation, the user shall have to hold the pump body with one hand and operate the pumping handle with the other hand. The user will get tired easily when operating a portable air pump in this manner. To overcome this problem, portable floor type air pumps are developed. When using a portable floor type air pump, the user can stop one end of the pump body against the floor and then reciprocate the pumping handle with one single hand. This operation method requires less effort. However, as the bottom surface area of this design is limited and the footplate is foldable, the structure of this design of portable air pump is unsteady and may vibration during operation, affecting operation smoothness. Further, in conventional designs, the pressure gauge is normally installed in the pump body. When the pump body is kept in vertical and stopped against the floor, the user cannot view the readings of the pressure gauge. To facilitate viewing the readings of the pressure gauge, U.S. Pat. No. 6,558,129 discloses an air pump entitled “Air pump having pressure gauge thereon”, in which the pressure gauge has a face marked with indication signs in the negative form; a cover is hinged to the base of the air pump for closing the pressure gauge and has a mirror disposed at the inner side thereof and adapted to reflect the image of the reading of the indication signs of the pressure gauge. However, when the cover is opened from the pressure gauge, it is not kept perpendicular to the pump body to facilitate viewing of the reflected image of the reading of the indication signs of the pressure gauge. If the cover is kept perpendicular to the pump body when opened, the mirror cannot reflect the image of the reading of the indication signs of the pressure gauge. Thus, when the cover is opened, it is kept at a sharp angle, for example, 45-degrees angle relative to the pump body. Keeping the mirror in this angular position causes user inconvenience in reading the readings.